tea1205at NXP Semiconductors, tea1205at Datasheet - Page 6

• Manufacturer Part Number: tea1205at
• Description: High Efficiency Dc/dc Converter
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Synchronisation function
In continuous conduction mode, the converter
switching frequency is synchronized to the signal at the
SYNC input, provided that this signal is present and its
frequency is 13 MHz. The switching frequency will than
be 2
the sync pin. If no sync signal is applied (Sync pin H
or L), the converter’s switching frequency will be
around 203 kHz, equally to behaviour at 13 MHz sync
input frequency, but with a larger tolerance. When this
function is not used, the SYNC pin must be tied to pin 3
or pin 6.
Power switches
The power switches in the IC are one N-type and one
P-type MOSFET, having a typical pin-to-pin resistance of
0.12
current in the switches is 1.0 A.
Temperature protection
At too high device temperature (typical 165 C), the
converter stops operating. It resumes operation when the
device temperature falls below 165 C again. As a result,
low-frequent cycling between on and off state will occur.
It should be noted that in the event of device temperatures
around the cut-off limit, the application differs strongly from
maximum specifications.
Current limit
If the current in the N-type power switch exceeds the limit
which is set by the value of the external resistor, current
ramping is stopped immediately, and the next switching
phase is entered. Current limitation is required to enable
optimal use of energy in Li-ion batteries, and to keep
power conversion efficient during temporary high loads.
Furthermore, current limitation protects the IC against
overload conditions, inductor saturation, etc.
1998 Mar 24
High efficiency DC/DC converter
6
times smaller than the applied input frequency at
and 0.16
respectively. The maximum average
6
Behaviour at input voltage exceeding the specified
range
In general, an input voltage exceeding the specified range
is not recommended since instability may occur. However,
at an input voltage equal to or higher than the target output
voltage plus the diode voltage drop, but lower than 6 V, the
converter will stop switching and the external schottky
diode will take over, resulting in V
diode voltage drop (see Fig.8).
handbook, halfpage
Fig.3
low power
mode
medium power
mode 1
medium power
mode 2
low DC current
high DC current
Coil current waveforms in the various power
modes.
Preliminary specification
o
time
equalling V
TEA1205AT
increasing
MGK924
load
i
minus the